BRENDAN SMIALOWSKI/AFP/GettyImages(WASHINGTON) -- President Obama launches a two-day education bus tour on Thursday, focused on access to and the rising cost of college.

But before they can even get to college, American students are struggling just to get the skills they need to get in. And an effort to raise the bar and standardize what children learn in grade school is hitting significant headwinds.

"States have been implementing this over the last two years," said Maria Voles Ferguson, executive director of the Center for Education policies. "Now people are starting to get that, 'Oh these things are here and they're changing my school and changing my community.'"

The new and somewhat surprising opposition to Common Core Standards is perhaps one of the least publicized political battles this year. But it serves as a critical backdrop for Obama's efforts to make the economic argument that affordable college is not only good for middle-class pocketbooks but also economic competitiveness.

The Common Core, which was borne out of conversations between governors, chief state school officers and private foundations, aimed to set uniform standards for what kids should learn by the time they left high school -- benchmarked to foreign competitors that are outpacing the U.S. in educating their work force.

When the idea was first being drafted in 2009, dozens of governors signed on -- Republican and Democrat. And it's not hard to see why.

In its annual report this week, the college prep company that makes the ACT found that only 26 percent of students who take their test -- a requirement to get into some colleges -- met college ready benchmarks in English, reading, math and science.

Obama has made the argument countless times from the presidential podium that the U.S. curriculum needs to catch up with the rest of the world -- as had Presidents Bush and Clinton before him.

And for a while, it seemed that the states were following along. Forty-six of them and the District of Columbia signed on to the Common Core plan. Even critical Republicans like former Florida Gov. Jeb Bush were on board.

But a curious thing has happened: the common core has become just another political football.

"There has always been this concern that the federal government is trying to take over our schools," Furgeson said. "I'm not sure it's going to ever go away."

What has made its opponents livid isn't the higher standards. It is what they consider the intrusion of the federal government -- namely the Obama administration using the standards as a gateway to grants and waivers that exempt states and school districts from the more onerous provisions of the Bush-era No Child Left Behind law.

"When the administration stepped in and began tying federal funds to the Common Core, it quietly shifted from being voluntary to being de facto national standards for tests," said Lindsey Burke, policy analyst at the conservative Heritage Foundation.

The new regime, which nearly everyone acknowledges will be a sea change for the states that adopt it, is scheduled to be fully implemented by 2014.

And as the clock ticks closer to that deadline, the effort to stop the standards has accelerated at the state level.

Conservative groups like Florida Parents Against Common Core have made it their mission to reverse their state's stamp of approval on the plan. And prominent Republicans such as Sen. Marco Rubio, R-Fla., and Sen. Lamar Alexander, R-Tenn., have staked their conservative credentials on opposing the Common Core push, even as the Republican governors in their states support the effort.

Thirteen states -- including Indiana, Pennsylvania, Alabama and Ohio -- have now either opted out of the standards or taken steps that call in to question whether they will go through with implementing the new standards and assessments.